Transform key in dict to attribute in dataclass

[davetapley]

I'm getting JSON from an API which looks like this:

{
  "alert1/622": {
    "meta": {
      "sensor": {
        "name": "Battery Voltage"
      },
      "station": {
        "name": "Redrock Repeater "
      },
  }
}

And I'd like to parse in to:

@serde
@dataclass
class Sensor:
    id: str
    meta: Meta | None
    data: Data | None

Is there a way to transform the "alert1/622" key into the id attribute,
without manually doing an orjson.loads, transforming the dict, and using from_dict?

[yukinarit]

@davetapley

How about using dict?

from dataclasses import dataclass
from serde import serde
from serde.json import from_json, to_json

s = """
{
  "alert1/622": {
    "meta": {
      "sensor": {
        "name": "Battery Voltage"
      },
      "station": {
        "name": "Redrock Repeater "
      }
    }
  }
}
"""

@serde
@dataclass
class Entity:
    name: str

@serde
@dataclass
class Meta:
    sensor: Entity
    station: Entity

@serde
@dataclass
class Data:
    pass

@serde
@dataclass
class Sensor:
    meta: Meta | None
    data: Data | None

d = from_json(dict[str, Sensor], s)
print(d)
print(to_json(d))

Output

{'alert1/622': Sensor(meta=Meta(sensor=Entity(name='Battery Voltage'), station=Entity(name='Redrock Repeater ')), data=None)}
{"alert1/622":{"meta":{"sensor":{"name":"Battery Voltage"},"station":{"name":"Redrock Repeater "}},"data":null}}

[davetapley]

Of course! Thanks!
I was so fixated on dataclass it never occurred to me to just give the dict[str, Sensor] constructor to from_json.

---

.... but I expanded on that and found what might be a bug:

class SensorInfo(dict[str, Info]):
    @classmethod
    def load(cls, s):
        return from_json(cls, s)

⬆️ this looks like it works, but Info is a dict 🤔

Using dict constructor and then 'casting'toSensorInfo` seems to work though:

        return cls(from_json(dict[str, Info], s))

[yukinarit]

@davetapley Can you please show me the complete code?

This worked for me.

@serde
@dataclass
class Sensor:
    meta: Meta | None
    data: Data | None

class SensorInfo(dict[str, Sensor]):
    @classmethod
    def load(cls, s):
        return from_json(cls, s)

d = SensorInfo.load(s)
print(d)
print(to_json(d))

[yukinarit]

Or if you have only 1 pair of data and using dict doesn't make sense, please consider using rename.

@serde
@dataclass
class Entity:
    name: str

@serde
@dataclass
class Meta:
    sensor: Entity
    station: Entity

@serde
@dataclass
class Data:
    pass

@serde
@dataclass
class SensorData:
    meta: Meta | None
    data: Data | None

@serde
@dataclass
class Sensor:
    sensor_id: SensorData = field(rename="alert1/622")


d = from_json(Sensor, s)
print(d)
print(to_json(d))

Output

Sensor(sensor_id=SensorData(meta=Meta(sensor=Entity(name='Battery Voltage'), station=Entity(name='Redrock Repeater ')), data=None))
{"alert1/622":{"meta":{"sensor":{"name":"Battery Voltage"},"station":{"name":"Redrock Repeater "}},"data":null}}